Toxoplasmosis in Cats: Symptoms and Treatment

Toxoplasmosis in cats is caused by the protozoal parasite Toxoplasma gondii. It is a relatively common disease found worldwide in animals, birds, and humans. The disease is generally mild in cats, but it is zoonotic, meaning it can be transmitted to people.

Although toxoplasmosis is a legitimate concern for pregnant people and their babies, certain precautions can help reduce exposure in humans.

What Is Toxoplasmosis in Cats?

Toxoplasmosis in cats is a relatively common disease caused by the protozoal parasite Toxoplasma gondii. It can be found worldwide in animals, birds, and humans.

The disease is generally mild in cats, but because it is zoonotic (meaning it can be transmitted to people), it is important to recognize its health implications.

You may have heard that if you're pregnant or plan to become pregnant, you should re-home your cat because of toxoplasmosis. This is a legitimate concern for pregnant people and their babies, but there's no reason to re-home your cat because of the condition.

What Causes Toxoplasmosis in Cats?

Cats can become infected with Toxoplasma gondii by ingesting feces containing infectious oocysts, eating infected tissues such as uncooked meat or wildlife, or through passage of tachyzoites from mother to fetus during pregnancy.

How the Toxoplasma gondii Lifecycle Works

The parasite affects two different kinds of hosts:

• Definitive hosts: Hosts necessary for the sexual reproduction of the parasite. Oocysts (similar to eggs) are then shed in the feces. Cats are the definitive hosts for the parasite.
• Intermediate hosts: Hosts in which the parasite reproduces asexually, or by producing “daughter” organisms that split from the “mother” organism.
  
  Parasites in intermediate hosts pass through two distinct life stages: tachyzoites (fast-reproducing) and bradyzoites (latent form). Non-feline animals can serve as intermediate hosts and become infected.

Cats can become infected by all three T. gondii life stages: oocysts, tachyzoites, and bradyzoites.

What Happens After a Cat Is Infected?

Once in the feline intestines, T. gondii can produce oocysts, which are then passed in the stool, or replicate to become tachyzoites, which migrate throughout the body and affect multiple organs.

Symptoms vary depending on which organs are affected.

When Do Toxoplasma Oocysts Become Infectious?

Oocysts passed in the feces are not infectious at first. They become infectious after one to five days, when they undergo a process called sporulation.

These oocysts can remain in the environment for many months.

What Are the Symptoms of Toxoplasmosis in Cats?

Symptoms of toxoplasmosis in cats are often mild and can go unnoticed in otherwise healthy cats. 

When symptoms occur, they depend on the organ(s) affected by the tachyzoite.

Symptoms may include:

• Lethargy
• Decreased appetite
• Weight loss
• Fever
• Difficulty breathing
• Jaundice
• Behavioral changes
• Vision loss
• Weakness
• Neurologic signs, including:
  • Lack of coordination or circling
  • Neck pain
  • Seizures

How Is Toxoplasmosis in Cats Diagnosed?

Veterinarians may diagnose toxoplasmosis in cats using antibody titer testing, cerebrospinal fluid (CSF) testing, and tissue samples (biopsies). Diagnosis can be challenging because oocysts are rarely identified in routine stool exams.

Stool and Antibody Testing

The identification of oocysts in a stool sample does not mean that a cat needs to be treated.

Antibody titer testing (a test to determine infections) can be performed to help exclude the disease if the result is negative or aid in determining the likelihood of infection if the result is positive.

Cerebrospinal Fluid and Tissue Testing

A cerebrospinal fluid (CSF) test examines the fluid that surrounds the brain and spinal cord. CSF and tissue samples (biopsies) can be analyzed for the presence of tachyzoites.

How Is Toxoplasmosis in Cats Treated?

Treatment for toxoplasmosis in cats usually consists of a two to four-week course of the antibiotic clindamycin and may be combined with other therapies, including supportive care.

It has been reported that cats shed oocysts only once in their lifetime because they develop immunity after the initial infection.

Antibody testing can help confirm whether your cat has been previously exposed.

How To Reduce Human Exposure to Toxoplasmosis

You can take precautions to minimize exposure to toxoplasmosis through your cat, food, gardening, and litter box care.

• Give your cat properly cooked or commercially prepared food.
• Prevent your cat from going outdoors and ingesting wildlife.
• Wash fruits and vegetables thoroughly.
• Avoid raw or undercooked meat and associated kitchen utensils, and wash your hands thoroughly with soap and water after contact. Thoroughly cooking food will eliminate any tachyzoite or bradyzoite cysts it may contain.
• Wear gloves while gardening and keep sandboxes or other “cat-suitable” toilet locations covered.
• Scoop the litter box daily. It takes one to five days for oocysts to become infectious, so day- to week-old feces pose a much higher risk.

Toxoplasmosis Precautions for Pregnant or Immunocompromised People

If you are immunocompromised or immunosuppressed, it is recommended that someone else scoop the litter box for you.

Pregnant women should be more vigilant because T. gondii can cross the placenta, and babies who are exposed can have significant birth defects.

Recovery and Management of Toxoplasmosis in Cats

Most cats infected with toxoplasmosis do not develop the disease itself. Recovery and prognosis depend on the cat's immune response, with young and immunocompromised cats less likely to survive.

Most infected cats essentially act as carriers. It would be rare for a cat to be shedding oocysts while also suffering acutely from the disease.

Immune Response and Dormancy

If a cat develops an infection and tachyzoites begin migrating throughout the body, the immune system mounts a resistance.

If the immune response is effective, the tachyzoites are forced back into the bradyzoite stage and lie dormant in unaffected organ(s). They may remain dormant for many years and are unlikely to cause future problems.

Toxoplasmosis in Young and Immunocompromised Cats

Young and immunocompromised cats, including cats with FeLV or FIV, are less likely to survive because they are less able to build a sufficient immune response and defense.